Abstract
Rhodonite and pyroxmangite have been found to coexist in nature. These minerals were investigated by the single-crystal X-ray method and with an electron probe microanalyser. The two phases intergrown hold a certain orientational relation with each other, and the chemical compositions of the two phases are different from each other, the parts rich and poor in Ca corresponding to rhodonite and pyroxmangite respectively. This orientational relation was found to agree with that caused by an artificial thermal transformation of pyroxmangite into rhodonite, and to be in conformity with the principle of densest-zone preservation. The mechanism of intergrowth of the two phases in nature was explained with a reasonable process of cation and silicon migration in pyroxmangite to form rhodonite.
